Broken-down joint protection in coded track circuit signaling systems



' M. A. SCHEG BROKEN-DOWN JOINT PROTECTION IN CODED TRACK CIRCUIT SIGNALING SYSTEMS Filed Feb. 9, 1946 ISOCT H15 A TTORNE Y i atented Oct. 9, 1 951 BROKEN-DOWN JOINT PROTECTION IN CODED TRACK CIRCUIT SIGNALING SYSTEMS Marcian A. Scheg, Rochester, N. Y., assignor to Generalltailway Signal Company, Rochester,

Application February 9, 1946, Serial No. 646,625

7 Claims. 1

This invention relates to coded track circuit signalling system for railroads, and it more particularly pertains to a system for prevention of faulty operation of the signals in case of a breakdown in the insulation of the rail joints between two adjoining track sections.

It is possible to a certain extent to protect against controlling a track circuit code receiver by track circuit codes impressed upon an adjoining track circuit, when the rail joints break down, by the staggering of the polarity applied to the track rails for the respective track sections, and employing biased polar track relays. However, certain conditions arise where the polarities cannot be staggered between adjoining track sections,'and there are conditions Where it is desirableto use both polarities selectively in order to obtain the required number of distinctive signal controls for transmission through the track rails.

In view of the above conditions, an object of the present invention is to provide a system, irrespective of track circuit polarity, for the protection of signals against faulty operation due to broken down insulation of rail joints in such'a manner-as to provide restrictive indication for the signals governing trafiic through the particular adjoining track sections involved in the broken-down rail joints. Such protection requires the use of only one additional relay over those generally required for the transmission and reception of track circuit codes, and such protection is provided without the restrictive control of the signals cascading back through the track sections which are used in the control of signals not involved in the portion of the trackway having the broken-down insulation in the rail joints.

Another object of the present invention is to detect broken-down insulation in the rail joints upon passage of a train before the signal governing entrance to the occupied track section can be operated to provide a false indication. This is accomplished by picking up a lock-out relay when the first pulse is received in a track section after passage of a train, and holding such lock-out relay up to prevent the reception of pulses if the rail joints are broken down.

Another object of the present invention is to check the operation of the lock-out relay used for broken-down joint protection each time a train passes through the track section with which it is associated. In other words, the reception of the track circuit code, and the clearing of a signal after passage of a train is dependent upon proper response of the look-out relay associated with the code receiver used in controlling that signal,

such lock-out relay responding only momentarily if there is no broken-down joint condition.

Other objects, purposes and characteristic features of the present invention will be in part obvious from the accompanying drawing, and in part pointed out as the description of the invention progresses.

In describing the invention in detail, reference will be made to the accompanying drawings in which corresponding parts are designated by like letter reference characters which are generally made distinctive by reason of preceding numerals indicative of the signal location with which such parts are associated, and in which:

Fig. 1 illustrates the coded track circuit signaL ling system provided by the present invention as applied to a typical stretch of track signalled for eastbound traffic; and

Fig. 2 illustrates a modified form of the coded track circuit signalling system provided by the present invention for a typical stretch of track signalled for eastbound traflic.

The illustrations employed in the disclosure of this embodiment of the present invention have been arranged more to facilitate the disclosure as to the mode of operation and the principles involved than for the purpose of illustrating the specific construction and arrangement of parts that would be employed in practice. Thus the relays and their contacts are shown in a conventional manner, and the symbols and are employed to indicate connection to the positive and negative terminals respectively of suitable batteries or other sources of direct current, and the circuits with which these symbols are used always have current flowing in the same direction.

With reference to Fig. 1, this embodiment of the present invention is provided for a stretch of track signalled for eastbound trafiic (to the right), the stretch of track illustrated comprising the track sections IT, 2T and 3T. Each of the respective track sections has a signal for governing eastbound trafifilc through the track section. such signal being provided with control apparatus such as the apparatus specifically shown associated with the signal 2. Thus, for the purpose of simplification of the disclosure of the present invention, the description of the invention will be set forth more specifically with reference to the apparatus provided at the location of the signal 2, and it is to be understood that similar apparatus is provided at each of the ignal locations associated with other track sections along the trackway. It is also to be understood that various modifications in the track circuit, such, for eX- ample, as the provision of cut sections at various points, can be provided in accordance with the usual practice with repeating means provided for repeating the codes through the track sections adjoining each cut section.

It will be apparent as the description progresses that the system provided according to the present invention can be used with various types of signals, such for example, as signals of the searchlight, semaphore, position light, or color light types. The signals illustrated in Fig. 1 are of the color light type having individual color light units R, Y and for the respective danger, caution and clear indications. The modified form of the present invention illustrated in Fig. 2, however, shows the signals as being of the searchlight type.

At the left-hand end of the track section 2T, the code following track relay 2TB, is connected across the track rails, and such relay can be of the biased polar type generally employed in coded-track circuits.

A home relay 2-H which is associated with the control of signal 2 is suihcientl slow acting to be steadily energized in response to the pulsing of the contacts ill and I I of the track relayZTR, such relay being energized through a decoding transformer in the usual manner, theprimary winding ll of the transformer being energized with alternatepolarities in accordance with the pulsing of contact if] of the relay 2TB, and the secondary winding of the transformer being effective to provide for the direct current energizatio-n of the relay 2H, through the rectifying contact I i of the relayZTR. Another secondary winding of the decoding transformer provides energization for the relay 2D through a tuned circuit and rectifier unit tfil'lDU topro ide that the relay =23 is maintained steadil picked up, only in response to the reception of a 180 track circuit code which is used for governing the clear indication of thessignal 2.

The relay iCP is a code transmitter relay used in the transmission of a track circuit code from right to left in the track section VI, such relay being-effective to energize-that track section for each pulse upon closure of its front contact i3 to-connect the track battery 14 across the track .rails at the-right-hand end of the track section The relay lCP is selectively controlled as .to whether it is totransmit a 180 or a 75 code in accordance with the contac 55 of the relay 2H. That is, when the relay 21-1 is picked up, the relay lCP is selected to transmit a 180 code in accordance with pulses provided by the coding contact |8llCT which is generally operated by a code oscillator or someother suitable impulse formingdevice. However, if the back contact it of the relay 21-1 is closed, the rela [CF is selected to transmit a 75 code in accordance with re pulsing of the contact 750T.

The relay 2L0 is provided for the'purpose of protecting thesignal .2 against being controlled to;provide afalse indication in case the insulated rail joints between the track sections IT and 21 should break down. This relay, as'shown in Fig. 1, is of the magnetic stick type which is a relay having a polar structure to be distinctively responsive to energization of the respective polarities, and to be maintained during periods of deenergization in the last position to which its contacts have been operated. With reference to Fig. 2, the relay ,2LO is provided fora similarpurpose. to the relay ,ZLO shown in Fig. 1, but

is provided with a modified means of energizatlcn, and such modified control provides that the relay 2LO is not required to be of the magnetic stick type, but can be provided as a simple neutral relay.

It will therefore be seen that with the stretch of track unoccupied by trains, the code transmitter relays GP for the respective track sections -:.are normally active to transmit a 180 code in accordance with the energization of a circuit similar to the circuit provided for the rela ICP and winding of relay ICP, to

Thus it is assumed that the relay 2GP at the right-hand end of track sect-ion 2T is active to transmit a 180 code in the manner corresponding to that just described for the operation of the relay ICP for the transmission of a 180 code in the track section IT. Therefore thecontacts ii] and H of the relay .ZTR are normally pulsing at a 180 rate to provide for the picking up of the relays 2H and 2D. In accordance with the energization of these relays a circuit is closed to energize the green lamp G of signal 2, such circult extending from including front contact ii of relay 2H, front contact at of relay 2D, and the lamp G of signal 2, to-

Upon passage of a train, the entrance of an eastbound-train into the track section 2T causes the contacts i-G and H of the relay 2TB, to become inactive by shunting the track rails of the track section, and therefore causes the relays EHand 2D tobe dropped away. Upon such conditions the opening of front contact i? of relay 2H extinguishes the green lamp G in the signal 2 and a circuit isclosed at back contact ll of relay 2H to provide for the energization of the red lamp R in that signal.

With the relay 2H dropped away, the relay iCP becomes active for the transmission of a code in the track section IT because of the energization of a circuit extending from including coding contact 750T, back contact i5 of relay 2H, polar contact it of relay 2L0 in its left-hand position, and windingof relay iCP,to It will be readily apparent as the eastbound train progresses and occupies the track section 3T, that the relay 2GP becomes active to transmit a 75 code under similar conditions to those just described with respect to theopera- .tion of the relay iCP.

Considering the eastbound train to have .left the track section ET, the removal of the rail shunt from-the track relay 2'IRprovides that such relay is picked up in response to a'code pulse applied tothe track rails of the track section-2T by thelower terminal of the primary winding of the decoding transformer including polar contact '28 of the relayZL-O in its left-hand position,-b ack contact 2! of relay=2I-I, and winding of relay 2L0, to It is a characteristic of the magneticstick type of relay to operate its polar contacts undersuch conditions, even though the operation ofisuch contacts opens the energizing circuitjor that relay su'ch in the present condition where the operation of the polar contact 29 to its righthand position is effective to open the operating circuit just described for the relay 2L0. It will be noted that the closure of front contact it of relay 2TB. energizes the primary winding I2. of the decoding transformer with a polarity to aid the induced voltage in operating the relay 2L0 in case relay 2TB. should close its front contacts.

before relay 2L0 is actually picked up.

Upon the operation of the polar contact 22 of the relay 2L0 to its right-hand position, a circuit is closed by which the relay 2H can be energized in accordance with the energization of the secondary winding 23 of the decoding transformer. Such circuit extends from the rectifying contact I I of the track relay 2TB, including the winding of relay 2H, and polar contact 22 of the relay 2L0 in its right-hand position, to the center connection of the secondary winding 23 of the decoding transformer. When the relay 2H is picked up in response to the pulses received at the left-hand end of the track section 2T, the closure of a stick circuit at front contact 24 of such relay shunts the contact 22 of the relay 2L0 out of the control circuit just described for the relay 2H. The picking up of relay 2H also opens the circuit for the red lamp R of signal 2 at back contact I1 and closes a circuit for the yellow lamp Y of that signal at front contact II, such circuit including back contact I8 of relay 2D.

The picking up of relay 2H closes a circuit at front contact 2| to provide for energization of the lock-out relay 2L0 with a polarity to operate its polar contacts to their left-hand positions. Such circuit extends from (-I-) including polar contact I5 of relay 2L0 in its right-hand position, front contact 2| of relay 2H, and Winding of relay 2L0, to It will be noted that the operation of the contacts of relay 2L0 to their lefthand positions in accordance with the energization of this circuit opens the circuit just described for the relay 2L0 at polar contact I6 in its righthand position, and thus the relay 2L0 is restored to its normal position with its winding deenergized.

It will be noted that the closure of contact of It of the relay 2L0 in its right-hand position also applies energy directly to the code transmitter relay ICP, and therefore is eifective to hold such relay in its picked up position as long as the relay 2L0 is maintained in its operated position. This ready energization of the relay ICP is provided as a part of the function of the relay 2L0 in case the insulation of the rail joints breaks down in a manner to be hereinafter described. However, upon considering the normal operating conditions of the system as described above, the relay ICP is steadily energized in response to the operation of the look-out relay 2L0 after passage of a train through the track section 2T, only for the time required to pick up the relay 2H, and thus restore the contacts of the relay 2L0 to their lefthand positions.

Inasmuch as the characteristics of the slow acting H relays are such that the pick-up time is shorter than the drop-away time, the H relay (not shown) at the left-hand end, of the track section IT will not have time to drop away due to the steady energization momentarily applied to the track section IT by the code transmitter relay ICP during the time required for the picking up of the relay 2H and the operation of the relay 2L0 to its left-hand position to open the steady energization circuit for relay ICP at contact I6. Such characteristicsof the H relays prevent the possibility of the momentary dropping away of an H relay for a track section when steady energization is momentarily applied at the entrance end of the track section in accordance with the initial reception of code after passage of a train by the code receiving means for the next track section in advance.

It is to be. understood that the mode of operation of the relay 2L0 coresponds to that provided at each of the signal locations when the track relay 'IR at such location again becomes active after passage of a train. This particular mode of operation is provided in such a manner as to check the operation of such LO relay by requiring the proper operation of that relay in order that the home relay H for that signal location may be picked up. The manner in which the lock-out relay L0 is effective in providing a lock-out to prevent faulty operation of the signals will be hereinafter considered.

It will be readily apparent that a the train progresses beyond the track section 3T, the relay 3H is picked up in a manner corresponding to that described by which the relay 2H was described as being picked up when the track section 21 was assumed to have become unoccupied in the rear of the train. The relay 2GP then becomes active to transmit a 180 code in the track section 2T, and in accordance with the reception of such code at the left-hand end of that track section, the relay 2D is picked up, and the shifting of contact I8 of such relay is effective to cause the energization of the green lamp G of signal 2 and the deenergization of "the yellow lamp Y of such signal in an obvious manner.

Having thus considered the general mode of operation of the system when proper insulation is provided between the respective track sections, it will be assumed that the rail joints become broken down between the adjoining track sections IT and 2T, and it will be assumed that an eastbound train is occupying the track section 2T to provide a shunt on the track relay 2TR. -It has been described that under such conditions the relay ICP is active to transmit a code in the track section IT, and, assuming the rail joints between the track sections IT and 2T to be broken down, the '75 code thus applied to thetrack section IT is also applied to the track section 2T. As the train progresses, the shunt which it applies across the track relay 2TB. becomes less effective, and the relay 2TB, may then become energized in response to one of the pulses applied to the track rails of track section IT.

Upon the picking up of relay 2TB, under such conditions, the opening of back contact In of that relay provides for the energization of the relay 2L0 with a polarity to operate its contacts to their right-hand positions in a manner Which has been heretofore described. In accordance with the closure of contact I6 of relay 2L0 in its righthand position, steady energy is applied to the relay ICP, and thus the track section IT becomes steadily energized in accordance with the closure of front contact I3 of relay ICP. It is therefore provided that the relay 2TB is maintained steadily energized under such conditions, and there is no pulsing of the contacts I0 and II of relay 2TB to provide for the picking up of relay 2H. This being the case the closure of back contact I! of relay 2H is effective to maintain the signal 2 at danger because of the energization of the red lamp R of such signal. Obviously, the

relay 2L0 is maintained. in its right-hand .posie' tion steadily because the energization of its restoration circuit is dependent upon the closure of front contact 2i of. the relay 2H, which cannot be .picked up as long as the broken-down joints exist between the adjoining track sections IT and 2T. 7

Upon considering the circuit organization, and the mode of operation provided in the control of the look-out relay 2L0 as described .above, it will be noted that two specific conditions are re,- quired to exist at the same time in order to provide for the operation of that relay. .Oneof such conditions is that the relay 2H must be dropped away, which is a condition obtained only when the track relay 2TB is inactive, and the second condition is that the back contact lot the relay 2TB must be opened to provide the pick-up pulse. It is therefore provided that the relay 2L0 can be picked up only upon the opening of the circuit for the primary winding l2 of the decoding transformer by the opening of back contact ,H! of, the track relay 2TB at a time when the code receiving relay 2B is dropped away. It

is this particular combination that provides a means to preventthe cascading of. the. lock-out relays LO for signal locations in the rear of a location having broken-down insulation in the rail joints.

More specifically, it will be assumed that the joints between the track sections 2T vand 3T are broken down and an eastbound train. has proceeded in the track section 3T to allow the relay 3TB. to be picked up in response to a pulse applied to the track section 2T by thccodc transmittcr 2GP. Under these conditions, the relay 20? has been active for the transmission of a 75 code. for some time prior tothc response of the track relay 3TH to a pulse of that code, thus providing that the home relay 2H at the left-.- hand end of the track section ET is picked up under these assumed conditions, and the lockout relay 2L0 has been actuated and restored upon passage of the train out of the track section 2T in a manner which has been described when considering the normal operation of the system. In accordance with the steady energizetion of the track section 21", however, the relay 2-H is dropped away, but the look-out relay 2L0 cannot be picked up at that time because there 4 is no pick-up pulse created for such relay by the opening of back contact 18 of relay 2TB due to relay 2TB having been picked up prior to the dropping away of the home relay 2H. By this arrangement it is provided that the signal 2 is put to stop if the rail joints are broken down between the track sections 2'1 and 3'1, but the present invention is illustrated, such form rproviding a general mode of operation in the protection of signals against faulty operation due to broken-down rail joints similar to the mode of operation described in detail for the embodi- Therefore it is believed unnecessary to describe specifically all the circuits involved in the control of the signals, and reference will be more particularly made to the ment shown in l.

manner in which the circuits shown in Fig. :lare modified to p ovide for the control of the n ut a lock-out relay 2110 as compared to the mag= neticestick lock-out. relay ZLQ shown in vFig. 1..

It will be no d that the s nals shown l e- .2 are of the searchlight type,, and th s type of?! signal has been shown so as to illustrate the manner in which a signal repeater relay such as the relay 2YG-P can be used in checking he operation of the lockeout relay 2140 I It will be readily apparent that the track relay 2TB and the relay 2H are controlled in a manner corresponding to that specifically described with reference to Fig. l, and corresponding ref- .erence characters hav been used for the contacts involved in the circuits for these relays, the front neutral contact 275 of the relay 2L0. being substituted 01" the contact 22 of the magnetic-stick. relay 210 shown in Fig. l. The signal repeater relay T16? is controlled in the usual manner .to be picked up when the signal is either at caution or clear. The relay '2YGP is therefore normally energized by a circuit extending from (-1-), including contact 26 of the mechanism of signal 2 in its clear position, front contact 2? ,of the relay 2H, and winding of relay ZYGP, to The inclusionof contacts 23 and .2501? the relay ZYGP in the control of the relay 2D checks the operation of the signal 2 to its caution position and also checks the operation of the relay 2H before the relay 2D is allowed to be energized upon the reception of a 180code.

T consider specifically the mode of operation of the system disclosed in Fig. 2, it will be assumed that passage of a train into the track section 2T has shunted the track relay 2TB, to cause the dropping away of the relay 2H and 2D. When the train leaves the track section 2T, the picking up of the relay 2TB in response to the '75 code applied at the right-hand end of the track section causes the picking up of the relay 2LO by the energization of a circuit extending from the lower terminal of the primary winding IQ of the decoding transformer including the half-wave rectifier 39, upper winding of relay 2LO and back contact M of relay ZYGP, to It will be noted that the inclusion of the haltwave rectifier 39 in this circuit provides that :the relay 2L0 cannot be responsive to energy of positive polarity applied at back contact it) of the relay 2TB when that back contact is closed.

The picking up of the relay 2L0 under such conditions closes a stick circuit for that relay to maintain it picked up until the signal 2' ha had its mechanism operated to either a caution or clear position to pick up the repeater relay ZYGP. eucl'l stick circuit extends from including back contact 32 of relay 2YGP, front con-tact 33 of relay 2LO and lower winding of relay 21.0

When the relay 2H is picked-up in response to code pulses received by the track relay 2TB, the closure of iront contac-t 2A of relay 2H shunts the contact 25 of relay 2L0 out of-tlie circuit required for the picking up of the relay 2H, and therefore provides that the dropping awayof the relay 2L0 upon the opening of its stick circuit at back vcontact 32 .of relay EYGP will not afiect the control of the relay 2H. It will he therefore apparent that the general. mode of operation of the neutral relay BLD upon passage of a train under conditions where therail joint are not brokendown is similar to the modelof operation which has been heretofore described-for the mag.-

nctic stick relay ZLO-nnder similar traflic .con-

ditiqns.

To consider the --.conditions involved. upon the passage of a train with" the rail joints-broken down, according tothe modified form of the intact ID of relay 2TB causes the picking up of relay 2LO because the relay ZYGP is dropped away at that time-in accordance with the signal 2 being at stop. The picking up of relay 2L0 closes a stick circuit which has been described for that relay, and also'closes a-circuit to steadily energize the code transmitter relay ICP. Such circuit extends from including back contact 34 of relay 2H, front contact 35 of relay 2LO and winding of relay ICP, to In accordance with the energization of this circuit, the contact [3 of the relay [CF is maintained steadily closed, and therefore the relay 2TB. is maintained steadily energized by energy fed from the track battery It t the track section IT. Thus, with relay 2TB steadily energized, the relay 2H remains dropped away; the signal 2 remains at danger; and the signal repeater relay 2YGP remains dropped away. Therefore the relay 2LO is maintained picked up by its stick circuit closed at back contact 32 of relay ZYGP as long as energy is fed to the track relay ZTR through the broken-down rail joints.

It is believed that it will be readily apparent that the conditions involved in preventing the picking up of lock-out relays for track sections in the rear of the broken down joints for the Having thus described a system of broken-down joint protection for a coded track circuit signalling system for a particular stretch of track as one specific embodiment of the present invention, it is desired to be understood that this form is selected to facilitate in the disclosure of 51 the invention rather than t limit the number of forms which the invention may assume, and it is'to be understood that various modifications, adaptations and alterations may be applied to the specific form shown to meet the requirements of practice without in any manner departing from the spirit or scope of the present invention except as limited by the appending claims.

What I claim is:

1. In a coded track circuit signalling system of the character described for a stretch of track having a signal for a given direction of trafiic with a track section in advance and another in the rear thereof and with both sections having code pulses applied thereto, code receiving means at said signal operated by code pulses in said advance section, decoding means associated with said code receiving means, electro-responsive means for governing the response of said decoding means to the operationof said code receiving means, such electro-responsive means having normal and operated positions, means for energizing said electro-responsive means to actuate it to said operated position in response to the operation of said code receiving means only if said decoding means has been inactive for a period of time, means for initially rendering said decoding means active in response to the operation of said code receiving means by a track circuit code only if said electro-responsive means is in said operated position, means for restoring said electro-responsive means to said normal position when said decoding means becomes active, means for steadily energizing the track rails of said rear track section when said electro-responsive means is in said operated position, and signal clearing means for clearing said signal only when said decoding means is active, whereby in the event of broken down insulated rail joints the application of steady energy to the rear track section acts upon the code receiving means of the advance track section in a manner to render said decoding mean inactive resulting in said signal being held at stop, and whereby the clearing of said signal cannot beeffected by said decoding means unless said electro-responsive means has been actuated to its operated position and returned to its normal position subsequent to the passage of a train through the advance track section.

2'. In a coded track circuit signalling system, two adjoining track circuit sections separated by insulated joints, a signal located adjacent said insulated joints, code transmitting means associated with the section to the rear of said signal and acting when rendered effective to apply code pulses across the rails of that section adjacent said insulated joints, code receiving means associated with the section in advance of said signal and located adjacent said insulated joints for receiving legitimate code pulses from the leaving end of that section, a two position relay acting in one position to cause said code transmitting means to be rendered effective so as to transmit different distinctive codes in accordance with trafiic conditions in said advance section, said two-position relay acting in its other position to render said code transmitting means ineffective, and circuit means for governing the energization of said two-position relay to cause its actuation to said other position upon each initial reception by said code receiving means but causing said relay to be operated to its said one position only providing reception by said code receiving means continues for a time sufiicient to determine that a legitimate code is being received.

3; A circuit organization for detecting broken-down insulated joints at signal locations in a coded track circuit signalling system for railroads comprising for each signal location, a code following track relay for the forward tra'ck section at that signal location, a slow-release relay energized only if said track relay is deenergized after each energization within a limited time for governing the signal, a lookout relay acting when actuated to cause steady energization of the track rails of the rear track section at said signal location to test the integrity of the insulated joints, circuit means temporarily effective for a time less than release time of said slow-release relay for actuating said lockout relay upon energization of said track relay while said slow-release relay is deenergized, means for retaining said lockout relay in its actuated condition until restored, and means for restoring said lockout relay as soon as said slow-release relay becomes energized.

4. In a circuit organization for detecting broken-down insulated joints at each signal location in a coded track circuit signaling system for railroads comprising, a code following track relay for the forward track section at a signal location, decoding means governed by said track relay and in. cluding a decoding transformer and a slow-release relay maintained energized only by coded operation of said track relay, a ECOdB transmitter for 1 l supplying coded or steady energy to the track rails of the rear track section, a lookout relay acting in the actuated position to operate said code transmitter to maintain steady energization of the track rails of the rear track section, circuit means for actuating said lockout relay by a voltage induced in a winding of said decoding transformer only if said slow-release relay is deenergized, and means for restoring said lockout relay from its actuated condition upon energization of said slow release relay.

5. A circuit organization for detecting brokendown insulating joints at each signal location in a coded track circuit signalling system for railroads comprising, a code following track relay connected across the track rails of the forward track section at a signal location, a decoding relay maintained energized only in response to the coded operation of said code following track relay, a code transmitter for applying code pulses to the track rails of the rear track section at said. signal location, a lockout relay having normal and operated positions, circuit means for actuating said lockout relay to its operated position upon energization of said code following track relay after it has been inactive for a time and said decoding relay is deenergized, circuit means for operating said code transmitter to maintain steady energization of the track rails of the rear track section when said lockout relay assumes its operated position, and circuit means for restoring said lockout relay to its normal position upon energization of said decoding relay in response to coded operation of said code following track relay.

6. In a coded track circuit signalling system for railroads, a circuit organization for detecting failure of the insulated joints at a signal location separating a forward track section from a rear track section comprising, a code following track relay for the forward track section, decoding means governed by said track relay and including a slow-release relay governing the indication of the signal and maintained energized only by coding operation of said code following track relay, a code transmitter for applying code pulses to the rear track section at a code rate determined by the condition of said slow-release relay, a lockout relay of the magnetic stick type having normal and actuated positions and acting when actuated to operate said code transmitter to maintain a steady energization of the track rails of the rear track section, means for temporarily supplying actuating energy to said lockout relay upon energization of said code following relay after it has been inactive for a time and said slow-release relay is deenergized, and circuit means responsive to the energization of said slow-release relay for supplying restoring energy to said lockout relay for causing its operation to said normal position.

7. In a circuitorganizationfor detecting brokendown insulated joints between a forward track section and a rear track. section at a signal location in a coded track circuit signalling system, a code following track relay at the signal location for the forward track section, decoding means governed by said track relay including a slowrelease relay energized only if said track relay is intermittently energized and deenergized in response to code pulses, said slow-release relay acting to govern the indications of the signal at that location, code transmitting means for applying code pulses to the rear track. section in accordance with the condition of said decoding means, a lookout relay having an operated and a restored position, said lockout relay in its operated position preventing operation of said code transmitting means and causing steady energization of the rear track section, circuit means temporarily effective'upon picking up of said track relay for actuating said lockout relay to its operated position only providing said slow-release relay is in a deenergized position, other circuit means. for actuating said lockout relay to its restored position when said slow-release relay is in an energized position, and circuit means preventing the initial energization of said slow-release relay only when said lockout relay is in its operated position.

MARCIAN A. SCHEG.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,215,904 Kemmerer Sept. 24, 1940 2,235,134 Allison et a1 Mar. 18, 1941 

